Sound recording composition and method of making the same



Patented May 11, 1954 SOUND RECORDING COMPOSITION AND METHOD OF MAKING THE SAME Richard G. Rowe, Bedding Ridge, Conn, assignor to Dictaphone Corporation, Bridgeport, Conn.

No Drawing.

Original application May 15, 1948,

Serial No. 27,37 0. Divided and this application February 13, 1952, Serial No. 271,415

7 Claims.

' i This invention relates to a novel anti-static agent adapted to be incorporated in a sound-recording medium to reduce the tendency of static electrical charges to accumulate on the surfaces of such a medium, and also to sound-recording media incorporating such an anti-static agent. The antistatic agent of the present invention is particularly useful for reducing the accumulation of static charges on the well-known wax recording cylinders, and will be illustratively described in that environment. The phrase soundrecording wax will be used hereafter to designate the material of which such cylinders are made, although as is well known sound-recording waxes are ordinarily largely composed of metallic soaps, higher fatty acids, or both, and may contain no wax at all in a strict chemical sense.

The present application is a division of my pen-ding application, Serial No. 27,370 filed May 15, 1948, and is particularly directed to sound recording compositions containing anti-static agents and methods of making such compositions, as distinguished from the anti-static agent itself whichfis claimed in the parent case.

For many years sound-recording wax cylinders have been used for a variety of sound-recording purposes. As ordinarily used, such cylinders are mounted on a horizontal rotating man drel of a dictating machine, and a laterally movable sound-responsive stylus cooperates with the rotating cylinder to cut a helical sound track in the surface'thereof. As an incident of this cutting action short, curly fibers of the wax material are removed from the surface of the cylinder, which fibers are sometimes referred to as chips, and a container or chip collector is usually provided beneath the cylinder to collect those chips that fall off the cylinder. It is, of course, desirable that all of the chips fall off the cylinder as soon as they have been formed so that they may be collected and disposed of in an orderly manner, but unfortunately there is a tendency under normal circumstances for the majority of the chips formed to continue to adhere to the cylinder surface. Although the reasons for the adherence of the chips to the surface of the cylinder are not completely understood, my investigations indicate that the principal reason for this undesired adherence of the chips is the accumulation of a static electrical charge on the surface of the cylinder.

' The removal of the chips from the surface of the cylinder is desirable for a variety of reasons. The cylinders are usually kept in cylindrical containers having an interior lining made of a 1ibrous fabric, and if the chips are not completely removed from the cylinder surface, they may be transferred to the interior of the container. Continued use of a container that has been contaminated with chips may cause the sound record to be scratched or otherwise deformed as the cylinder is inserted into or withdrawn from the container. If the chips are not removed by contact with the interior of the container, they may interfere with transcription of the sound record. Moreover, the adhering chips ar generally untidy since, if they do not fall into the chip collector of the dictating machine for disposal in a controlled manner, they have a tendency to fly off in the atmosphere and adhere to clothing, carpets and the like.

It is accordingly an object of the present in vention to provide a wax sound-recording medium in cylindrical or other form that is of such a character that chips cut from the surface thereof by a sound-responsive stylus do not tend to adhere to the surface of the medium. It is another object of the invention to provide an antistatic agent adapted to be incorporated in a sound-recording wax to reduce the tendency of static electrical charges to accumulate on the S111- face of the sound record. It is a further object of the invention to provide a sound-recording wax incorporating such an anti-static agent. It is still another object of the invention to provide a method of making such an anti-static agent and a method of incorporating it effectively into a sound-recording medium. Other objects of the invention will be in part obvious and in part pointed out hereafter.

The objects of the present invention may be achieved in general by providing a sound-recording wax containing a relatively small quantity of N-cyclohexyl lactamide. I have found that the tendency of static electrical charges to collect on the surface of a sound-recording wax containing a small proportion of N-cyclohexyl lactamide, is materially reduced, and that when this compound is incorporated in the wax nearly all of the chips formed by the action of a soundresponsive stylus thereon fall off as soon as they are formed. The quantity of the lactamide in corporated in the sound-recording wax may vary from 2% to 10% by weight, although in most cases preferred results are obtained by using about 4% by weight of the lactamide.

The present anti-static agent is preferably added tothewax while the wax is in molten condition-and prior tothe time that it is cast into a 3 cylinder. Although N-cyclohexyl lactamide may be added to the molten wax as such, I prefer rather to add to the wax cyclohexylamine lactate which, during the process of manufacturing the wax cylinder, is converted into the lactamide.

So far as I am aware, cyclohexylamine lactate is a new compound that has not previously been prepared. It is a white crystalline substance which has a melting point between 95 C. and 96 C. and may be readily and conveniently prepared by a method described below.

In order to point out more fully the nature of the present invention, the following illustrative procedure is given for making thecyclohexylamine lactate and also for incorporating itina sound-recording wax to produce a 'sound recording medium having anti-static properties: An electrically heated or steam heated open stainless steel vessel equipped with a motor driven agitator and forced ventilation is charged with 204 lbs. of 80% lacticacid. Using gentle agitation with no heat applied, 196 lbs. of cyclohexylamine is added at the rate of 100 lbs. per hour. With this rate of addition of the cyclohexylamine the reaction temperature normally remains in therange of about 120 F. to 180 F. The quantity of cyclohexylamine added is about in excess of that stoiohiometrically required to re-- act with the lactic acid present.

When the addition of the cyclohexylamine is .complete,'the batch is heated to a temperature of about 265 F. and maintained at that temperature for about four hours. The hot reaction products are then poured into shallow pans and allowed to cool over night, whereupon they solidify. The resulting crude cyclohexylamine lactate is a tan waxy material which may be purified by. repeated washing with cold acetone. In most cases, however, purification is unnecessary and the product can be used in thecrude state in the formulation of an anti-static sound-recording wax.

As stated above, the purified product is a white crystalline material having a melting point between 95 C. and 96 C. It is very soluble in .water and also soluble in most of the common organic solvents. Its specific conductivity, although not comparable with that of a metal, is substantially higher than the conductivity of other chemically related materials.

The cyclohexylamine lactate as thus formed may be incorporated in a conventional soundrecording wax, for example, the wax formula disclosed at page 35 of The Reproduction of Sound by Henry Seymour (1918), in the following manner: A suitably heated vessel is charged with 3,333 lbs. of S. Stearine (commercial stearic acid) and the S. Stearine is melted. To the molten S. Stearine a solution of 208 lbs. of 98% caustic soda in 525 lbs. of water is slowly added. As the causticsoda solution is added, neutralization of the S. Stearine occurs and the mixture is heated to such an extent as to remove all water from the resulting soap mixture.

After completion of this neutralization step, 178 lbs. of red lead is added to the mixture in the reaction vessel. The addition of the red lead may be efiected by removing a small quantity of the molten soap mixture from the heated vessel and mixing the red lead in powder form there with, after which the mixture of red lead and soap is added to and mixed with the main body of material in the vessel.

When the red lead has been incorporated into the molten soap, 212.5 lbs. of cyclohexylamine -mixture is cast into cylinders in the usual manner, and the cylinders machined to form the desiredsounderecording surface.

Cylinders 'made in accordance with the foregoing procedureare strikingly superior to conventional cylinders in respect to the extent to which chips fall off the surfaces thereof when they are cut by a sound-responsive stylus. Moreover, tests have shown that the electrical conductivity of the wax is appreciably increased by incorporation of the present anti-static agent therein.

It is, of course, to be understood that the foregoing detailed procedure is illustrative only and that numerous changes may be made therein without departing from the scope of the invention. As indicated previously, the desired result may be achieved by adding either N-cyclohexyl lactamide or cyclohexylamine lactate .to the molten wax. However, there is some advantage in using the lactate since it is easier to make than the lactamide and is automatically converted into the lactamide in the course of the formulation of the sound-recording wax. Many different wax formulae have been previously proposed for sound-recording purposesand my experiments indicate that the present anti-static agent can be used in any of these known formulae to improve the anti-static properties of the resulting sound-recording wax.

Since many embodiments might be made of the present invention and since many changes might be made in the embodiment disclosed herein, it is to be understood that the foregoing description is to be interpreted as illustrative only and not in a limiting sense.

I claim:

1. A sound-recording medium having antistatic properties, said medium comprising a sound-recording wax composed predominantly of metal soaps and containing a small proportion of N-cyclohexyl lactamide.

2. A sound-recording medium having antistatic properties, said medium comprising a sound-recording wax composed predominantly of metal soaps and containing from 2% to 10% by weight of N-cyclohexyl lactamide.

3. A sound-recording medium having antlstatic properties, said medium comprising a sound-recording wax composed predominantly of metal soaps and containing about 4% by weight of N -cyclohexyl lactamide.

4. A wax sound-recording cylinder composed predominantly of metal soaps and having incorporated therein a small quantity of N-cyclohexyl lactamide to confer anti-static properties on said cylinder.

5. The method of making a sound-recording medium having anti-static properties which comprises preparing a melt of a sound-recording wax composed predominantly of metal soaps and, mixing therewith a small amount of cyclohexylamine lactate, heating the resulting mixture to convert said lactate to the lactamide, and cooling and casting said mixture to form, a solid sound-recording medium.

6. The method of making a sound-recording medium having anti-static properties which comprises preparing a. melt of a sound-recording wax composed predominantly of metal soaps and, mixing with said molten wax between 2% and 10% by weight of cyclohexylamine lactate, heating the resulting mixture to convert said lactate to a lactamide, and cooling and casting said mixture to form a solid sound-recording medium.

7. The method of making a sound-recording medium having anti-static properties which com- 10 prises heating a mixture of fatty acid, caustic alkali, and paraflin wax to form a molten mass, adding to said molten mass from about 2% to 10% by weight of cyclohexylamine lactate, heating the resulting mixture to convert said lactate to a. lactamide, and cooling and casting the 'resulting mixture to form a solid sound-recording medium.

No references cited. 

1. A SOUND-RECORDING MEDIUM HAVING ANTISTATIC PROPERTIES, SAID MEDIUM COMPRISING A SOUND-RECORDING WAX COMPOSED PREDOMINANTLY OF METAL SOAPS AND CONTAINING A SMALL PROPORTION OF N-CYCLOHEXYL LACTAMIDE. 